lavfi/aevalsrc: correct the supported sample format

The source supports *planar* double, fix regression introduced by me in
4d4098da.

libavfilter/asrc_aevalsrc.c

@@ -185,7 +185,7 @@ static int config_props(AVFilterLink *outlink)
 static int query_formats(AVFilterContext *ctx)
 {
     EvalContext *eval = ctx->priv;
-    enum AVSampleFormat sample_fmts[] = { AV_SAMPLE_FMT_DBL, AV_SAMPLE_FMT_NONE };
+    enum AVSampleFormat sample_fmts[] = { AV_SAMPLE_FMT_DBLP, AV_SAMPLE_FMT_NONE };
     int64_t chlayouts[] = { eval->chlayout, -1 };
     int sample_rates[] = { eval->sample_rate, -1 };